US3814985A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electronic flash unit having protective circuit for flash terminating switch
Assignee: Metz Apparatewerk Inh Paul Metz
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Filing: 1972-10-17
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Granted: 1974-06-04
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Expires: 1992-10-17
Abstract
Abstract A semi-conductor switch interrupts the flashtube current, thereby terminating the flash when a blocking voltage is applied to its anode. The blocking voltage is derived from a capacitor. If the capacitor has not sufficiently recharged following a previous flash, the semi-conductor switch is not completely blocked causing it to burn out. Therefore, a transistor is provided whose emitter-collector circuit short-circuits the ignition capacitor when conductive. The base of the transistor is connected to the charging circuit for the capacitor furnishing the blocking voltage in such a manner that the transistor remains conductive until the capacitor charging current has decreased to a predetermined current.
Inventors
- 👤 W Pecher
- 👤 H Schottner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 11:41
CPC Classifications
H; H05; H05B; H05B41/00; H05B41/14; H05B41/30; H05B41/32; H05B41/325
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
203 words
In an electronic flash unit, in combination, a source of electrical energy; flash generating means connected to said source of electrical energy for furnishing a light flash upon receipt of an ignition signal; ignition circuit means connected to said flash generating means for furnishing said ignition signal upon external activation; first switch means connected to said flash generating means, said first switch means having at least a first electrode and having a first state during said flash, for switching to a second state blocking said flash upon application of a predetermined voltage to said first electrode; terminating capacitor means connected to said source of electrical energy in such a manner that the voltage across said terminating capacitor means varies as a predetermined function of time following termination of a flash; means for applying said voltage across said terminating capacitor means to said first electrode upon receipt of a terminating signal; means for furnishing said terminating signal at the end of a desired exposure time; and additional circuit means interconnected between said terminating capacitor means and said ignition circuit means for inhibiting the operation of said ignition circuit means until said voltage across said terminating capacitor means is substantially equal to said predetermined voltage.
Claim 2
Dependent Claim
203 words
In an electronic flash unit, in combination, a source of electrical energy; flash generating means connected to said source of electrical energy for furnishing a light flash upon receipt of an ignition signal; ignition circuit means connected to said flash generating means for furnishing said ignition signal upon external activation; first switch means connected to said flash generating means, said first switch means having at least a first electrode and having a first state during said flash, for switching to a second state blocking said flash upon application of a predetermined voltage to said first electrode; terminating capacitor means connected to said source of electrical energy in such a manner that the voltage across said terminating capacitor means varies as a predetermined function of time following termination of a flash; means for applying said voltage across said terminating capacitor means to said first electrode upon receipt of a terminating signal; means for furnishing said terminating signal at the end of a desired exposure time; and additional circuit means interconnected between said terminating capacitor means and said ignition circuit means for inhibiting the operation of said ignition circuit means until said voltage across said terminating capacitor means is substantially equal to said predetermined voltage.
Claim 3
Dependent Claim
24 words
An electronic flash unit as set forth in claim 1, wherein said first switch means is connected in series with said flash generating means.
Claim 4
Dependent Claim
43 words
An electronic flash unit as set forth in claim 2, wherein said first switch means comprises a semi-conductor switch means having an anode-cathode circuit connected in series with said flash generating means and having a control electrode connected to said ignition circuit means.
Claim 5
Dependent Claim
36 words
An electronic flash unit as set forth in claim 3, wherein said first electrode of said first switch means is said anode and wherein said predetermined voltage is the voltage for blocking said semi-conductor switch means.
Claim 6
Dependent Claim
64 words
An electronic flash unit as set forth in claim 4, wherein said ignition circuit means comprise ignition capacitor means for furnishing an ignition voltage when charged; and wherein said additional circuit means comprise means for preventing the charging of said ignition capacitor means to said ignition voltage until said terminating capacitor means is charged to a predetermined capacitor voltage corresponding to said predetermined voltage.
Claim 7
Dependent Claim
50 words
An electronic flash unit as set forth in claim 5, further comprising charging circuit means connected to said terminating capacitor means for furnishing a charging current thereto; and wherein said ignition circuit means comprise second switch means responsive to said external activation, for initiating said light flash upon activation thereof.
Claim 8
Dependent Claim
45 words
An electronic flash unit as set forth in claim 6, wherein said additional circuit means comprise third switch means connected to said second switch means, said third switch means having a conductive state, for short circuiting said second switch means when in said conductive state.
Claim 9
Dependent Claim
43 words
An electronic flash unit as set forth in claim 7, wherein said third switch means comprise additional semi-conductor switch means having a controlled circuit conNected in parallel with said second switch means and having a control electrode connected to said charging circuit means.
Claim 10
Dependent Claim
82 words
An electronic flash unit as set forth in claim 8, wherein said additional semi-conductor switch means comprise transistor means, wherein said controlled circuit is the emitter-collector circuit of said transistor means and wherein said control electrode is the base of said transistor means; further comprising connecting means for connecting said base of said transistor means to said charging circuit in such a manner that the voltage at said base varies as a function of said charging current of said terminating capacitor means.
Claim 11
Dependent Claim
37 words
An electronic flash unit as set forth in claim 9, wherein said charging circuit means comprise voltage divider means having a voltage divider tap; and wherein said connecting means connects said base to said voltage divider tap.
Claim 12
Dependent Claim
25 words
An electronic flash unit as set forth in claim 7, further comprising indicator lamp means connected in parallel with said second and third switch means.
References Cited (Backward Citations)
US3569779A
Cited
US3683233A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-06-03 | 1977-12-03 | 1978-06-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-06-03 | 1981-12-03 | 1982-06-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-06-03 | 1985-12-03 | 1986-06-04 | $7700.00 | Window Closed / Lapsed |